go to your local shop orpay online
If you are referring to buying paintballs as the original question then we've answered that, and it's not necessarily the best answer
Buying online or at a shop may mean you have a big box full of paintballs that you cannot use
I can go to bookers and buy a beer barrel for a bargain price. I cannot then take it to the pub, they won't let me use my own beer, I could drink it at home but I don't have the facilities to run my own barrel
Translate this to paintballs and I cannot bring paint to a punter site, I probably can't bring paint to many events, I don't play on private land
So though I could get very good paint deals along with my team mates, we will usually do that with the providers on site at events
Buying paintballs from anywhere other than in person means you are paying for delivery in one way or another. It will come by courier and the survival of the paint is dependant on the packing and the handling by the courier
Buy in person and you prevent the risk of courier damage but you still have to do the transporting and storage
The question is why do you want cheap paint?
To beat the prices of your local site is impractical - would you be allowed to use it?
For an event etc you can get the best vfm on the day (or preordered) from the site traders
Cheap paint will be 'less good', the only way you will make a significant real saving will be by buying pallet loads
For the cost of paint look up the paintball shop sites, EG £30 or £40 a case